This invention relates to chuck assemblies for tool bits and, more particularly to a quick release chuck adapted for releasing the bit from the chuck using one hand.
Tool bits include tools used for drilling, driving, fastener devices such as screws, nuts and bolts, and other work elements requiring rotational motion. The American National Standards Institute has a specification for such tools known as ANSI B 107.4-1982 which refers to driving and spindle ends for portable powered and hand held machines using tool bits. Tool bits in accordance with the standard have a hexagonally configured shank with a circumferential groove formed into the shank. The circumferential groove has a flat, bottom portion disposed between two radiused shoulder portions. The standard reflects a long term and pervasive use of such tool bits and the large inventory of tools available.
It has long been recognized that the ability to quickly change tool bits in the spindle of the power source is an advantageous feature. Numerous examples exist in the art of quick release tool chucks. Quick release chucks using spring biased sleeves disposed on a spindle are known in prior art.
One common method of using the spring biased sleeve to retain the tool bit in the chuck is by urging a ball into contact with the circumferential groove of the tool bit and maintaining the ball in position by a shoulder (or cam surface) mounted on the sleeve. The ball is urged into contact with the groove and maintained in position by a compression spring disposed between the spindle and the sleeve. A ring secured to the spindle limits the movement of the sleeve in one direction, and the compression spring limits the movement of the sleeve in the opposite direction.
The tool bit is prevented from being axially extracted from the chuck by the shoulder. The spring biased shoulder is urged against the ball which locks it against a retaining face. Attempting to extract the tool bit from the bore without release of the detent ball pulls the ball against the retaining face. Therefore the shoulder locks the ball into the circumferential groove. The resulting force prevents extraction of the tool bit from the shank receiving bore. To release the tool bit from the receiving bore the user must retract the sleeve. The retracted sleeve acts to compress the spring which removes the shoulder from the locking position and allows the ball to move out of the circumferential groove of the tool bit.
Since it is necessary to manually retract the sleeve against the force provided by the compression spring, the user must use both hands to remove the tool bit. One hand is used to provide a constant force to compress the spring, while the other hand removes the bit from the bore. This often causes problems for workers (i.e., construction workers and carpenters) who regularly change drill bits in numerous types of construction projects. The worker is often in a position where it is difficult to change the bit, such as on a ladder.
Changing the bit may not only be inconvenient, but also dangerous. The worker may attempt to move the sleeve against the compression spring with one hand, using his or her body (or some stationary object) to provide pressure force against the power tool while he or she removes the tool bit with his or her second hand. Alternatively, the worker may attempt to hold onto the power tool handle with one hand, and simultaneously attempt to retract and hold the sleeve in a compressed position while removing the tool bit with the other hand. These awkward methods of changing of the bit often result in the worker losing his or her grip on the bit or on the tool and dropping it. At the very least, dropping the tool or bit causes the worker the inconvenience of having to descend the ladder to retrieve the bit. At worst, the bit could fall onto someone standing below, causing serious harm.
The invention is a chuck assembly for a tool bit which includes a spindle with a quick release mechanism adapted to allow the user to place the chuck assembly in a lock mode or a loading and unloading position.
The tool bit includes a shank portion with a circumferential groove in accordance with the ANSI standard. A longitudinally extending bore is provided in the spindle for receiving the shank portion of the tool bit. A first detent ball is disposed in a radially extending bore communicating with the shank receiving bore.
A spring biased sleeve shoulder is selectivly urged against the first detent ball, locking it against a retaining face. Attempted axial extraction of the tool bit from the bore presses the ball against the retaining face, producing an opposite tangential force to the axial retraction force. Manually moving the sleeve shoulder by moving a sleeve compresses the spring and releases the tool bit. A second detent ball is in communication with the sleeve and a spring biased shuttle in the bore. A hollow disposed on the shuttle locks the sleeve in place, preventing the shoulder from locking the first detent ball against the retaining face.
Attempting to lock the first detent ball into position against the tool bit circumferential groove without retracting the second detent ball from engagement with the sleeve results in the loss of the opposite tangential force to the axial retraction force. When the sleeve is in a retracted position, the tool bit may be axially extracted from the shank receiving bore. The second detent ball must be disengaged from locking the sleeve in a retracted position before the sleeve can lock the tool bit into place.
The invention can be defined as an improvement to a chuck assembly of the type having a chuck hub with a longitudinally extending bore therein the longitudinally extending bore having a closed end, an open end, and a radially extending bit bore in communication with the longitudinally extending bore, and a bit ball movable in the ball bore between a first retracted position out of the longitudinally extending bore and a second engaged position partially in the longitudinally extending bore. The inventive improvement includes a shuttle slidably disposed in the longitudinally extending bore. The shuttle has a first longitudinally extending portion having a first lateral dimension and a second longitudinally extending portion having a second, smaller lateral dimension. The shuttle is movable longitudinally between a first release position and a second lock position. The inventive improvement also includes a compression spring urging the shuttle away from the closed end of the longitudinally extending bore, and a shuttle ball disposed in a radially extending shuttle ball bore in the chuck hub which is in communication with the longitudinally extending bore of the chuck hub. The shuttle ball is movable in the shuttle ball bore between a first retracted position where the shuttle ball contacts the first longitudinally extending portion of the shuttle and a second extended position where the shuttle ball contacts the second longitudinally extending portion of the shuttle.
In one preferred embodiment, when the shuttle ball is in its second extended position, it extends further into the longitudinally extending bore than the bit ball, when the bit ball is in its second engaged position.
Preferably, the improved chuck hub also includes a sleeve movable relative to the chuck hub between a first shuttle release position and a second shuttle lock position. The sleeve has a first shuttle ball contact surface having a first radial dimension and a second shuttle ball contact surface having a second smaller radial dimension. The first contact surface engages the shuttle ball when the sleeve is in its first shuttle release position and the shuttle ball is in its first retracted position, and the second contact surface engages the shuttle ball when the sleeve is in the second shuttle locked position and the shuttle ball is in its second extended position.
The sleeve is preferably movable longitudinally relative to the chuck hub. The second shuttle ball contact surface on the sleeve is preferably an inner circumferential surface. In a preferred embodiment, the chuck hub has an outer circumferential surface adjacent the shuttle ball bore, and the inner circumferential surface of the sleeve has a slightly larger diameter than the outer circumferential surface of the chuck hub.
The present invention can also be defined as a locking chuck assembly for a tool bit shank of the type which has a circumferential groove disposed thereabout. The chuck assembly includes a chuck hub having a forward face and a fixed radial extension. A longitudinal bore is provided in the hub for receiving the tool bit shank, with the longitudinal bore having a terminating face. A shuttle is disposed in the bore. The shuttle has a bit end, a spring end, a forward lower face and a rearward interim face, and the shuttle is slidable along the longitudinal bore between a rearward position and a forward position. A shuttle spring is disposed between the spring end of the shuttle and the terminating face of the bore, with the shuttle spring acting to bias the shuttle to its forward position. A rear bore extends radially through the hub proximate the terminating face of the longitudinal bore so as to be in communication with the longitudinal bore, and a shuttle detent ball is disposed in the rear bore so as to engage the shuttle. A front bore extends radially through the hub proximate the forward face so as to be in communication with the longitudinal bore, and a bit detent ball is disposed in the front bore so as to engage the circumferential groove of the tool bit shank. A sleeve is disposed annularly about the chuck hub, and is slidable along the chuck hub between a tool bit loaded position and a load/unload position. A sleeve spring is disposed between the fixed radial extension of the hub and the sleeve to bias the sleeve toward its tool bit loaded position. When the sleeve is disposed in its tool bit loaded position, the shuttle is positioned in its rearward position such that the shuttle spring is compressed and the shuttle detent ball is engaged with the forward lower face on the shuttle so as to prevent the shuttle spring from moving the shuttle, while allowing the sleeve spring to bias the sleeve. When the sleeve is disposed in its load/unload position, the shuttle is positioned in its forward position such that the shuttle spring is less compressed than when the shuttle is in its rearward position and the shuttle detent ball is engaged with the rearward interim face on the shuttle and the sleeve is in a position to allow the shuttle spring to bias the shuttle away from the terminating face of the bore.